The present invention relates to a refrigerating device, and more particularly to a no-frost refrigerator, freezer or a combination refrigerator-freezer.
There are already known various constructions of refrigerating devices, such devices differing from one another mainly in the arrangement of the various components of the cooling apparatus. Such refrigerating devices include commercial or household refrigerators, freezers or combination refrigerator-freezers. The most recent development in the field of constructing refrigerating devices is the construction of so-called no-frost refrigerating devices in which formation of ice on the evaporator coils is to be kept to a minimum and such evaporator coils are to be periodically defrosted. Among the known and commercially available structurally different types of refrigerating devices, the present invention is concerned with such a refrigerating device in which the evaporator is located outside of the storage compartment of the refrigerating device, and the cooling of the interior of the storage compartment and of the contents thereof is accomplished by means of a stream of air which is deprived of some of its heat content in the evaporator, and which is forced to circulate through the evaporator and through the storage compartment.
There is already known a refrigerating device of a similar type in which the evaporator coil is periodically defrosted by means of an air stream which is withdrawn, during the standstill periods of the cooling device, from the storage compartment, and more particularly from a region thereof which is at a temperature above the freezing point, the stream of air being conducted over the heat-exchange surfaces of the evaporator, thus transmitting heat to the evaporator and defrosting the same. However, the available heat content of the air which is conducted through the evaporator in this manner is very minute, especially since the temperature of the air in the region from which it is withdrawn is only several degrees above the freezing temperature. In addition thereto, in many instances the volume of the air so conducted through the evaporator during the defrosting part of the cycle is very small. As a result of this, a very long time is needed for a complete defrosting of the evaporator. The time which would be necessary for completely defrosting the evaporator is in most instances longer than the standstill periods of the cooling apparatus, so that the evaporator is satisfactorily and completely defrosted only under the rarest circumstances. This, of course, brings about the danger that a layer of ice will gradually develop and grow on the evaporator. In addition thereto, this conventional arrangement requires complicated systems of regulating and control flaps or flap valves, and complex mechanisms are required for actuating such flap valves which are very expensive and prone to malfunction.
It has been already proposed, in order to expedite and accelerate the defrosting process in different conventional refrigerating devices of a similar type, to arrange a heating plate above the evaporator, the heating plate being heated with electric energy during the standstill times of the cycle of the cooling apparatus, the heating plate defrosting the evaporator coil in this manner. However, the energy consumption of the refrigerating device is considerably increased by using this electrical defrosting arrangement, so that the refrigerating device according to this proposal is substantially more expensive than other comparable devices in terms of construction costs and also in terms of the cost connected with operating the refrigerating device.